This invention relates generally to an improved optical lens or the like, and its related method of production and system components used in connection therewith, to provide improved depth of field, high resolution, and a one-way (directional perspective) and anti-glare effect with reduced diffraction.
In the prior art, anti-glare eyeglasses are well known and have been the subject of many patents. Generally, they have consisted of polarizing and/or occluding elements in or on the lenses such as gratings, louvers, or painted strips. Some of the latter have even had movable parts, but all of these occluding elements tended to obstruct vision. Polarized eyeglass lenses are generally only effective in reducing or eliminating glare from a certain range of angles, while allowing glare from a complementary range of angles to propagate through the lenses.
Pinhole eyeglasses, containing an array of pinholes in each lens in an opaque material, are known to achieve a remarkable focusing effect on both near and far images, with a keen resolution. However, this depth of field effect is adversely fragmented across the image panorama due to an uneven blending of the images from each pinhole. This problem is not present in smaller, closer-packed meshes such as nylon mesh stocking material, but here there is a diffusion effect. The holes in the mesh material do not possess a deep enough aspect ratio (depth divided by diameter) and the material does not possess the proper absorbent quality nor the same refractive index as the holes to eliminate the edge diffractions which cause the diffusion effect.
There is a special problem in creating a three-dimensional grid pattern of a relatively large depth and of a size that is small enough to be unnoticeable. Unless exotic methods are used, neither etching nor photographic techniques can achieve the necessary aspect ratio. The general rule in microlithography is that the depth of the detail cannot be held much past its width. Thus, for example, if the walls of the grid are 2 microns wide, and a mask containing this detail is contact printed onto a photosensitive substrate with collimated light, the detail will hold in the photosensitive substrate to a depth of about 2 microns before light diffusion destroys the detail. Holographic methods, in which the image is essentially "in focus" at any depth have been a way around this problem.
In accordance with prior holographic techniques, a laser beam has been divided into three or four parts and then recombined to achieve a grid pattern of interferometric fringes. See U.S. Pat. No. 4,496,216 (1985). The patterns were recorded on photographic film or plates or in a photoresist coating on a substrate. This provided the most practical means for writing a micron-sized mesh on a non-planar substrate such as a dome. This has been used for creating patterned induced transmission filters (ITFs) for missile nose cones. However, in these endeavors, the beams were usually projected from perhaps a meter away onto a dome-shaped substrate no larger than about 75 mm in diameter. No attempt was made to optically correct the distortion (stretching) effect of the intensity pattern where the incoming beams impinge at an oblique angle near the edges of the dome. Here the pattern will be skewed (elongated) in the direction of curvature.